Components in power generation systems, such as the turbine rotor blades and the turbine stator blades that are used in turbine equipment are exposed to an erosive environment in which these components are susceptible to erosion caused by water droplets in the steam and by fine dust from oxide scale. In particular, water droplets can cause substantial erosion of rear-stage turbine blades, where such water droplets are mixed into the steam for turbine driving. Erosion of turbine blades is problematic because it results in loss of blade chord width, loss of turbine efficiency, and fatigue breakdown of the blade brought about by erosion.
Various erosion preventive measures have been implemented to try to increase the durability of turbine components against erosion. One preventative measure involves using low heat-input build-up welding with a high energy-density heat source, such as laser beams to build up a plurality of single layers on the turbine component.
The residual stresses (tensile residual stresses) caused by contraction during build-up welding increases as the STELLITE® build-up amount becomes greater. These residual stresses, which are difficult to remedy significantly through heat treatment after build-up welding, may give rise to spalling in the form of peeling of the end of the build-up portion, or cracking at the weld metal portions, in the environment where the turbine operates.
Therefore, methods of forming a blade and a method for rendering a blade resistant to erosion that do not suffer from the above drawbacks is desirable in the art.